PER/LLK is a LACS (Locatable Address Conversion System) interface that utilizes the United States Postal Service's LACSLink™ data and technology.

Since the mid 1980s, the Enhanced 911 emergency response system has required the conversion of rural route-style addresses to city-style street names across the country. E-911 automatically associates a physical address with the telephone number from which an emergency call is made so that authorities can respond faster.

LACSLink™ data and technology enables mailers to automatically update their rural-style addresses with new, locatable city-style addresses in areas that are conducting E-911 emergency response address conversions. The LACSLink™ data currently contains over five million converted addresses. The LACSLink™ technology maintains the privacy and security of the data while allowing the access needed to convert outdated addresses.

Installation and use of PER/LLK is optional. However, a PER/LLK update is included with every PER/ZIP4 update.

Using PER/LLK with the PER/ZIP4 Batch Interface

When PER/LLK is installed you may see new informational messages (LLK) on the PER/ZIP4 Coding Report. This message will appear for each address that is LACSLink™ converted. You will also see the new PER/ZIP4 LACSLink™ Address Conversions Report. This report shows exactly which addresses in your file were changed as a result of LACSLink™ processing.

Using PER/LLK with the PER/ZIP4 Interactive and Callable Program Interfaces

When PER/LLK is installed, the PER/ZIP4 interactive interface will automatically LACSLink process all addresses entered. If LACSLink™ processing results in the conversion of an address, the message "Address LACSLink™ converted" will appear at the bottom of the screen.

When PER/LLK is installed, the PER/ZIP4 callable program interface will automatically LACSLink™ process all addresses passed into the interface. If LACSLink™ processing results in the conversion of an address, the converted (new) address will be returned and the informational code "LLK" will appear in the error code (ECOD##) field. It is important to note that just like "ALT" and "BNR", "LLK" is an informational code and not an error.